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Toward acceleration (1)

Toward acceleration (1). Shinji Machida ASTeC /STFC/RAL 18 November 2010. Contents. What we have achieved in longitudinal plane. Possible cause of beam loss. Possible source of closed orbit distortion. In longitudinal plane (1) what we expected.

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Toward acceleration (1)

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  1. Toward acceleration (1) Shinji Machida ASTeC/STFC/RAL 18 November 2010

  2. Contents • What we have achieved in longitudinal plane. • Possible cause of beam loss. • Possible source of closed orbit distortion.

  3. In longitudinal plane (1)what we expected • With 1.7 MV total voltage, we should see serpentine channel “deceleration”. Simulation with a momentum cut at 9.5 – 21.5 MeV/c

  4. In longitudinal plane (2)what we observed expected Experiment set1 Experiment set2 Experiment set3

  5. In longitudinal plane (3)simulation to reproduce experimental results Simulation with a cut of 15.5 – 21.0 MeV/c Experiment set1 Simulation with a cut of 14.5 – 21.0 MeV/c Simulation with a cut of 15.5 – 22.0 MeV/c

  6. In longitudinal plane (4)what we have achieved • Observed momentum gain or loss by rf voltage. • However momentum shift is limited +/- 2~3 MeV/c 15.5 – 21.0 MeV/c

  7. In longitudinal plane (5)conclusions • Synchrotron oscillation period shows that a beam sees ~1.7 MV rf voltage indeed. • Hard wall around 15.5 MeV/c and 21.0 MeV/c. • Number has an accuracy of +/- 1 MeV/c or even more.

  8. In longitudinal plane (6)with different lattice • Hardedge lattice is used in transverse. • Different lattice which gives the measured tune at 18.5 MeV/c shows different behavior in time of flight. • Serpentine channel does not appear with 1.7 MV. Tune adjusted at 18.5 MeV/c Initial hardedge

  9. Cause of beam loss (1)total tune vs momentum • Total tune becomes integer every ~2 MeV/c. • Not clear, but probably related to beam loss. Initial hardedge Tune adjusted at 18.5 MeV/c horizontal horizontal vertical vertical

  10. Source of closed orbit distortion (1)observed COD presented by Kelliher

  11. Source of closed orbit distortion (2)systematic gradient error by V-corrector • Shepherd calculated QF next to V-corrector has 1.7% stronger gradient. • There are 16 such QF. • This cannot cause vertical orbit distortion, but can do in horizontal.

  12. Source of closed orbit distortion (3)calibration with QD27 • Take a difference between 205 (B) and 220 (R) A.

  13. Source of closed orbit distortion (4)simulation results • Effect of different QD27 setting (+7.3%) can be reproduced by simulation. • Vertical spike should be something else. Red: COD by QD27 with +7.3% in simulation Green: difference between 205 A and 220 A

  14. Source of closed orbit distortion (5)simulation results • 1.7% stronger gradient of QF next to V-corrector does not enough to explain observed COD. • However oscillation phase is similar.

  15. Source of closed orbit distortion (6)alignment error of QFs • If 1mm (equivalent) alignment error of QF next to V-corrector, observed COD can be explained. • Oscillation phase is similar. Above COD is caused with 0.1 mm QF shift.

  16. Source of closed orbit distortion (6)summary • Gradient error of QF next to V-corrector does not explain the observed COD, but still suspicious. • For example, http://www.astec.ac.uk/intbeams/users/machida/doc/nufact/ffag/machida_20070307.pdf

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